Eight-unit code telegraph system



Aug. 23, 1932. A. F. CONNERY EIGH1'UNIT CODE TELEGRAPH SYSTEM Filed April 1, 1931 4 Sheets-Sheet 2 INVENTOR v ALDER E CQNNERY ATI'ORN Y Aug. 23, 1932.

A. F. CONNERY EIGHT-UNIT CODE TELEGRAPH SYSTEI Filed April 1, 1931 4 Sheets-Sheet 3 i FIG. 5

INVENTOR ma 5 couueav 23, 1932- A. F. CONNERY EIGHT-UNIT CODE TELEGRAPH SYSTEM 4 Sheets-Sheet 4 Filed April 1, 1931 w OE INVENTOR- ALDER E CONBEIQY ATI'ORN Y Patented Aug. 23, 1932 unrrso STATES PATENT OFFICE ALDER I. CONNEBY', OF BROOKLYN, NEW YORK, ASSIGNOB TO INTERNATIONAL GOM- MUNIOATIONS LABORATORIES, INC., 01 NEW YORK, N. Y, A CORPORATION OF NEW YORK EIGHT-UNIT OODE TELEGRAPH SYSTEM Application fled April 1, 1931. Serial No. 528,888.

This invention relates to communication systems and more particularly to prlntmg telegraph systems for operatlon over submarine cables or telegraph lines in which the attenuation increases very rapidly with an increase in signalling frequency.

Heretofo're, difliculty has been experienced in finding a code which was altogether suitable for use over communication lines of high attenuation, and particularly over long submarine cables. The five-unit two element code, which is generally used in land line machine telegraphy, is unsatisfactory by reason of its length when compared with the unequal length three-element cable code, the code combinations of which average 3.7 units in length. The three element cable code, which is now in general use, has, however, the disadvantage of having a no-current or zero 2 element which in itself is objectionable, and, in addition, the fact that the code has three elements rather than two lowers the frequency at which it can be satisfactorily used.

.It is therefore an object of this invention to provide a two-element code which will be suitable for high frequency transmission over lines of high attenuation.

A further object of this invention is a communication system in which either a six-unit 80 or a seven-unit two element code may be automatically translated into an eight-unit two element code and vice versa. A further object of this invention is a communication system adapted to utilize an eight-unit two element code in such a manner that the transmitted code will have the frequency of a four-unit code.

A further object of this invention is a communication system adapted to utilize a two element code having alternative combinations of opposite polarity for each letter.

The present invention is based on the use of an eight-unit two element code having alternative code combinations of opposite polarity for each letter, and in which no impulse of single unit length occurs other than at the beginning or end of a code combination. In the application of the invention to standard six-unit machine printing equipment, which is the preferred form of the invention, current is applied to either side of all the transmitting contacts according to the (polarit of the lastunit of the preceding co e com ination, as determined by the position-of a relay associated with the sixth pair of transmitting contacts, thus determining which of the two codecombinations will be set up on the transmitter contacts. The re-transmitting relay associated with the first transmitting contact of the distributor is operable from the common lead of one side of the transmitter contacts and, as a result, the first contact of the transmitter carries to the line an impulse of the same polarity as that of the last unit of the preceding code combination and thus assures the selection of the proper code combination at the receiving terminal. The siX units perforated in the transmitting tape are transmitted in the ordinary manner, except that an eighth unit is inserted between the fifth and sixth units of the six-unit code and its polarity determined by the setting of the fourth, fifth and sixth sets of transmitting contacts, the selection beingeifected by a special group of relays associated with these contacts. At the receiving terminal, the first impulse received determines the polarity of current to be applied to the common return of all the printer selector magnets and thereby determines which of the two code combinations is to be used. When a sixunit printer is employed, the sixth impulse received is not used, the printer selector magnets being operated from the second, third, fourth, fifth, seventh and eighth received impulses. Thus a six-unit two element code is automatically translated into an eight-unit two element code in which at least two impulses of the same polarity always appear together and which is used to operate a six magnet printer at the receiving station.

Fig. 1 sets forth an eight-unit two element code having alternative code combinations of opposite polarity for each letter and also shows the impulses which would be used in the application of the code to a six-unit communication system; I

Fig. 2 illustrates the application of the The invention will be more clearly under stoodif the above designated figures are considered in connection with-the following detailed description of the invention as applied to. a six-unit and to a seven-unit machine printing communication system.

I eight-wait lt'wo element code This invention covers a modified eight-unit multiplex code which is particularly adaptable to submarine cable or long line operation where the speed of transmission is seriously limitedby a rapid increase in attenuation when the signalling frequency is raised.

The code which forms part of this invention is a modified eight-umt two element code.

. The total number of combinations possible with an eight-unit code are 2 or 256. Inthe.

modified eight-unit code, only those code oombinations which contain no single-unit impulses,except at the beginningor end of a code combination, are used. Out of the 256 possible combination, there are 68 which meet these requirements.

It willbe obvious that if a letter combinatidn ending with a single negative unit wereto be followed by a letter starting with a positive unit, there would be an impulse of singleunit length transmitted. To avoid this difiiculty, two code combinations are assigned to each letter, which two combinations are identical except that the polarity of each unit in one combination is the exact reverse of the polarity of the corresponding unit in the other code combination. For example,

the two combinations. assigned to a certain letter might be and and the combinations assigned to another letter might be -+,and-+++.

The transmitter for use with this code is so arranged that, if the last impulse of the last character transmitted is positive, then the combination automatically chosen for the next letter will be the one which starts with a positive impulse. On the other hand, if the last unit of the last character is negative, then the combination starting with a negative impulse will be chosen for the succeeding letter.

Since two combinations are assigned to each character, the total number of characters which may be selected is only one-half that of the possible code combin atlons, or 34.

navaeea If, however, it is desired to operate a six-unit printer, then, of the eight units transmitted,

merely for the purpose of setting the printer so that it will respond-to. the proper one of the two combinations assigned to each letter and the sixth unit, while transmitted as usual, is-not utilized at the receiving end. An eightunit code which will be satisfactory for such a use will of necessity have fewer available code combinations.

' The total suitable combinations for such an eight-letter code, together with a tentative assignment of characters, are shown in Fig. 1. This code has 29 difierent combinations, which is the minimum that it is possible to conveniently use in operating this type of receiving printer. 26 of these combinations have been assigned to the letters of the alpha;

bet, the three remaining combinations having been assigned as follows: idle signal, letter shift and space, and figure shift. It will be noted that there are no impulses of single unit length other. than at the beginning or units 2', 3, 4, 5, 7 and 8 alone are used to operate the printer. The first impulse is used ending of a code combination and, when a message is transmitted, these single units at the'beginnin and ending of the combinations are linlied with signal units of'like polarity in the preceding and succeeding code combinations. Thus, while this code has been called an eight-unit code, it is really a fourunit code as far as the signalling frequency is concerned, since in transmission the shortest signalling impulse is two units and there will, therefore, not be more than four rever sals in polarity forany one code combination. For this reason this eight-unit code should be very easy on the duplex balance.

In comparing the modified eight-unit codewith the regular three element cable code, it would appear that the eight-unit code, which is practically equivalent to a four-unit code, would be inferior to the regular cable-code which averages 3.7 units per character. It should be remembered, however, that the proposed code has only two elements, positive and negative, while the regular cable code has three elements, positive, negative and zero,

and a higher signalling frequency can be realized with the code having the least number of elements.

Description of the Sim-unit transmitting system operating the perforator and it is, therefore,

necessary that the correct code combination be selected and transmitted automatically.

Referring to Fig. 2, a tape transmitter 1,

o erated' by a perforated tape, is shown.

he transmitter contact tongues 27 are lot ' operated by fingers (not shown) which feel for perforations in the tape which is passed through the transmitter. The cadence or operation magnet 8, which is operated from the distributor 9, steps the tape forward once for each revolution of the distributor brushes. This transmitter may be of any of the standard six-unit types, and since such transmitters are well-known in the art,-.it will not be described in further detail. A developed view is shown at 9 of a rotary transmitting distributor which 1s also wel known in the art and which has contact rings 10, 11, 24 and 13 arranged in palrs and is equipped with a brush arm carrying brushes 14 and 15 which join the various segments of the paired rings together as the brushes pass over them. The segments 16 23 of ring 13 are the transmitting segments and the solid ring 24 is connected to the cable over conductor 25. Brushes 14 and 15, which travel from left to right, are arranged to be driven at a very constant rate of speed. This constant speed is preferably attained by means of a phonic wheel motor controlled by a constant speed, electrically operated tuning fork as is customary in multiplex telegraph practice. Rings 10 and 11 are known as local rings and are used for completing local circuits and do not carry the current which is sent to the cable. The un-numbered segments of distributor 9 are not used in connection with any of the active circuits, but are used merely for the purpose of carrying brush 14 while it is passing from one live segment to another.

While this system is shown as applied to a single channel, it is readily adaptable to multi-channel operation.

Relay 26 is a polarized relay, the armature of which is capable of remaining upon either its spacing or marking contact when no current is passing through either of the windings 29 or 30. For the purpose of this description, it will be assumed that a current flowing from right to left through either of the windings will move the tongue to the marking contact, and that a current passing through either winding from left to right will move the tongue to the spacmg contact. The operation of this relay is determined by the polarity of the last unit of the preceding code combination and its function is to determine which of the two code combinations assigned to each character is to be used.

The remaining relays 3142 of Fig. 2 are all of the neutral or non-polarized type. Relays 3138 are re-transmitting relays, each of which is associated with one of the re-transmitting distributor segments 16--2 3. Relays 39, 40 and 41 are connected in series with locking relays 35, 36 and 37 respectively and jointly determine whether retransmitting relay 38, associated with relocking circuits of relays 35, 36 and 37 and their associated relays 39, 40 and 41. Operation of aim-unit transmitting system In order to follow the operation of the transmitter, let it be assumed that the word BE is to be transmitted. Referring to the code of Fig. 1, it will be seen that the perforated combination for the letter B will consist of a. single perforation which will permit the sixth pin of the tape transmitter 1, shown in Fig. 2, to rise, and this will cause tongue 7 to be pressed against the.lower or I marking transmitter contact. The remaining tongues 2-6 of the transmitter will remain against their upper -or spacing contacts. If it be assumed that the last signal impulse of the preceding code combination was such that the tongue of relay 26 was moved against its marking contact 28, as shown, then positive current is connected to the lower side of all the transmitter contacts. It will, therefore, be evident that relay 31 will not be energized, as this relay is connected by conductors 43 and 44 with all the upper or spacing contacts of the transmitter, which contacts are not connected with battery. When distributor brush 15 passes over the first transmitting segment 16, a positive impulse will be passed to the cable over the following circuit: 1

ground, positive battery 45, conductor 46, back contact of relay 31, conductor 48, segment 16, brush 15, ring 24, and conductor 25, as the tongue of relay 31 will be lying against its back'contact. It will be noted that transmitter contact tongues 2, 3 and 4 are connected directly with re-transmitting relays 32, 33 and 34 respectively, and that tongues 5, 6 and 7 are connected through the distributor with re-transmitting relays 35, 36 and 37 respectively. In the transmission of the combination for the letter B it will be apparent that relays 3236 will not be energized. When brush15 passes over the second transmitting segment 17, therefore, a positive impulse will be passed to the cable as follows: from positive battery 45 over conductor 46, conductor 64, back contact of relay 32, conductor 65, segment 17 brush 15, ring 24 and conductor 25. In like manner, when brush 15 passes over segments 18 and 19, positive impulses are also transmitted to the cable from positive battery 45, over conductor 46,

conductor 66 and 67, back contacts of relays;

.33 and 34, and conductors 68 and 6.9, respectively. Durin the time, however, that the brush was 'assmg over transmitting segments 16 19, t e local brush 14 passed over segments 5560 and in doing so momentarily connected tongues 5, 6 and 7 to re-transmitting relays 35, 36 and 37, respectively. These relays are so arranged that they are capable of being energized and of locking up in an energized position. Tongue 7 is, however, the only tongue that is connected with battery and therefore re-transmit'ting relay 37 and tors 72 and 73, back contacts of relays and 36, and conductors 74 and 75, but when the brush passes over segment 23,v negative battery will be transmitted to the cable from negative battery 76, conductor 77, conductor 78, front contact of relay 37 and conductor 79,

since relay 37 is energized.

It will be noted that the sixth transmittiiig segment 21 has not yet been accounted for. There is no tongue in the tape transmitter corresponding to this segment and the polarity of the impulse sent to the cable when the brush passes over segment 21 is determined by the position of re-transmittingrelay 38 which is controlled by the selecting relays 39, 40 and 41,-join'tly. In this instance, relays 39 and 40 are unenergized while relay 41 is energized. The operating circuit for relay 38 is, therefore, opened at the right-hand contact of relay 41 and relay 38 is therefore unenergized and a positive impulse is passed to transmitting segment 21 from battery 45 over conductor 46, conductor 80, back contact of relay 38 and conductor 81. It may be noted I I at this point that the tongues and. contacts of relays 39, 40. and 41 are connected among themselves and to battery 82 in a fashion such that relay 38, whose tongue is connected to segment 21, will always apply a polarity to segment 21 that will fit in with the combinations set up on segments 20, 22 and 23 in a manner to assure that there will be no impulse of single unit length transmitted. For example, if relays 39, 40 and 41 are all in un-' v operated position, relay 38 will also be unoperated. If, however, relays 39, 40 and 41 areall in an operated position, relay 38 will also be operated, or if relays 39 and 40 are operated and rela 41'unoperated, relay 38 will be energized. f, on the other hand, relay 39 is unogerated and rela 40 is o erated, then whet er or not relay 38 is to energized will be determined by the position of relay 41. I j

, During the time the transmitting brush 15 was assmg over segments 20'2 3,'the local brus 14 passed over segments 83 and 84 and in so doing ener 'zed the cadence ,or operating magnet 8 o the tape transmitter 1 over a circuit traced from ground, battery 85, conductor 86,'conductor 87, segments 83 and 84,

conductor 88- to magnet 8 and ground. The

operation of the cadence magnet steps the perforated tape ahead one letter and the combinations for the letter E now control the position of the tape transmitter tongues. During the time the transmitting brush was passlng oversegments 20'23, the local brush 14 also passed over local segments 89 and 90, momentarily completing a circuit from bat tery 85 over conductor 86, conductor 91, segments 89 and 90,-conductor 92 through the left-hand front contact of relay 41 which is will open the locking circuit of relays 35, 36

and 3 at contact 98, releasing any of these relays which are energized and permitting them to fall back to their unoperated 'positions.

The combination of letter E, now in tape transmitter 1, provides a setting in which the .fourth tongue of the tape transmitter is lying against its lower or marking contact while all the other tongues are lying against their upper or spacing contacts. Since the combination which was just transmitted for the letter B ended in an impulse of negative polarity, the combination to be selected for the letter E should be the one starting with a negative impulse. Such a selection was made at the end of the last code combination when the armature of relay 26 was moved to its spacing contact.

Referring to Fig. 1, it will be seen that the proper code combination to be transmitted comprises four units of negative polarity and two units of positive polarity followed by two units of negative polarity. Referring back to Fig. 2, it will be apparent that when transmitting brush 15 passes over segment 16, negative battery will be transmitted to the cable because the tongue of relay 31, which is now energized from battery 70,'is lying against its front or negative contact. It will be noted, that, since the armature of relay 26 is on its this delay and it will, therefore, remain unoperated. When the brush 102- passes over receiving segments 104 and 105, relays 115 and 116 are also connected into circuits containing opposing battery of the same polarity and W111 fail to operate for the same reason. As relay 114 fails to operate, positive battery from current source 131 will be passed over conductor 132 through back left-hand contact of relay 114 to the common return 133 of the printer selector magnets 119-124. When brush 102 passes over segments 106, 1 07 and 109, selector magnets 121, 122 and 123 res ectively will fail to operate, since both si es of their windings are momentarily connected to the same polarit of battery, as was reviously pointed out 1n connection with re ays 114, 115 and 116. It should be noted that the sixth segment 108 is not connected to any selector magnet since the sixth unit is not used-in the operation of the receiving printer. During the time that brush 102 was passing over segments 106--109, the local brush 112 passed over local segments 134-137. When brush 112 passed over se ments 134, 135, a circuit was closed as to lows: ground, ositive side of battery 131, conductor 132, ack left-hand contact of relay 115, conductor 138, segments 134,135 and conductor 139 to selector magnet 119 and so over common return 133, back left-hand contact of relay 114 and conductor 132 back to the positive side of battery 131. A similar circuit is closed through segments 136 and 137, back left-hand contact of relay 116 and selector magnet 120. Since both ends of these circuits lead to positive battery, selector magnets 119 and 120 will not be energized. When brush 102 passes over segment 110, the tongue of relay 111 will have moved over to its marking or negative contact and a circuit will be closed from ground through battery 140, the marking contact of relay 111, conductor 127, receiving ring 113, brush 102, segment 110, printer selecting relay 124, common return 133, backleft-hand contact of relay 114, conductor 132 and positive battery 131. Selector magnet 124 will, therefore, be momentarily energized and will trip the corresponding code bar of the printer. Immediately after brush 102 has left receiving segment 110, the local brush 112 passes over segments 141 and 142 and temporarily closes a circuit from ground, battery 143, conductor 144, conductor 145, segments 141 and 142 and conductor 146 through relay 117, thus opening the locking circuits for relays 114, 115 and 116, and releasing them in the event that they were energized. At the beginning of the next revolution of the brushes, brush 112 passes over segments 148 and 149, closing a circuit from ground, battery 143, conductor 144, conductor 150, segments 148 and 149, conductor 151 through printer operating relay 125 to ground, and the operation of printer operating ma et 125 initiates the mechanical operation. 0 printing the letter,

Assume now that the combination for the letter E is being received. The code combmation in this case consists of four units of negat ve olarity and two units of positive po ar ty ollowed by two units of negative polarity. Whenthe brush 102 passes over segment 103, the tongue of relay 111 will be lylng against the negative or marking contact and relay 114 will be energized over the circuit previously traced, since batteries 130 and 140 now connected in the circuit are of opposite polarities and therefore supplement each other. The left-hand tongue of relay 114 will now lie against its front or negative contact, thereby connecting the common return 133 of the printer selector magnets 119- 124 to negative battery 148 over conductor 149, front left-hand contact of relay 114 and common conductor 133. When the brush 102 passesover segments 104 and 105, relays 115 and 116, respectively, will be energized and locked up over the circuits previously traced and for the same reason that relay 114 was operated. When the brush 102 passes over segment 106, selector magnet 121 will not be energized, since the tongue of relay 111 is still lying against its negative contact and the common return wire for the printer selector magnets is connected to negative battery 148. When, however, brush 102 passes over segment 107, the tongue of relay 111 will have moved to its positive or spacing contact and selector magnet 122 will be momentarily energized by current from source 126, as common return wire 133 is connected with negative battery 148 and the batteries therefore supplement each other. The tongue of relay 111 will also be on its positive or spacing contact when brush 102 passes over segment 108,

but as segment 108 is not connected with a printer selector magnet, nothing happens. When the brush 102 passes over segments 109 and 110, the tongue of relay 111 will again be lying on its negative or marking contact and the selector magnets 123 and 124 will not be energized, as batteries 140 and 148 oppose each other. During the time that the brush 102 was passing over segments 106-110, the local brush 112 was passing over segments 134-137, thus connecting the left-hand tongue of relays 115 and 116 respectively to printer selector magnets 119 and 120. Since the left-hand tongues of relays 115 and 116 are both lying against their negative contacts and the common return of the printer selector magnet is also connected to battery of the same polarity, magnets 119 and 120 will not be energized. Immediately after the brush 102 has left segment 110, the local brush 112 will pass over segments 141 and 142, thereby energizing relay 117 over a circuit previouslfy traced, thus opening the looking circuits 0 relays 114, 115 and 116 at conspacing contact, the upper or spacing contacts of tape transmitter 1 are nowahve, while the lower or marking contacts are not connected with battery, and contact tongues 2, 3, 4, 6 and 7 are therefore connected to positive battery, while tongue 5 has no battery applied to it. lie-transmitting relays 32, 33 and 34, which are directly connected to tongues 2, 3 and 4, respectively, will be enerized and the tongues of these relays will consequently be lying against their front or negative contacts. When the brush 15 passes over segments 17, 18 and 19, negative battery will therefore be transmitted from battery 76 over conductor 77, conductors 99, 100 and 47, front contacts of relays 32, 33 and 34 and conductors 65, 68 and 69 respectively to said segments and so to the cable. During the time, however, that brush 15 was passing over segments 16, 17, 18 and 19, the local brush 14 passed over segments 55-60; and in doing so momentarily connected the windings of relays 35, 36 and 37 to the transmitter tongues 5, 6 and 7 respectively. As tongues 6 and 7 are connected with battery, relays 36 and 40,

and 37 and 41, will lock up in an energized position, while relays 35 and 39 will not be energized. When the transmitting brush 15 now passes over segment 20, positive battery will be applied to the cable from battery 45 over the circuit previously traced. When the brush 15 passes over segments 22 and 23, negative battery will be ap lied to the cable from battery 76, conductor 77, conductors 27 and 78, left-hand front contacts of relays 36 and 37 and conductors 75 and 79, respectively, to segments 22 and 23 and so to the cable. Asrelay 39 is unoperated while relays 40 and 41 are both operated, relay 38 will not be operated and its tongue will rest against the back or positive contact, so that when brush 15 passes over segment 21, a positive impulse will therefore be sent to the cable from battery 45 over a circuit previously traced. The transmitter operating magnet 8 and unlocking relay 42 will be energized, as described in connection with letter B, and relay 26 set for the next code combination. The above description traces the course of the letters B and E through the transmitting circuits.

View of a rotary receiving distributor 101 is shown. The brushes 102 and 112 are to 'be driven in such a manner that they will always he in synchronism with the brushes at the distant end of the cable and also that they will maintain such a phase relation with the received signals that when brush 102 is passing over segment 103, the first unit of the signal combination will be actuatin the tongue of line relay 111. Receiving rush 102 operates at the same speed as local brush 112 which passes over a series of local segments. As in the case ofthe transmitting distributor, the unconnected segments are merely used for the purpose of carrying the brushes between the live segments. Receiv ing rela 111 is a two-positionpolar relay,

the win ing of which is connected in series with the incoming cable 155, and the armature of which at all times places either positive or negative current on receiving ring 113. For the purpose of this description, it will be assumed that a positivesignal being 'sent over the cable will move the tongue of.

relay 111 to the left-hand or spacing position, and that a negative signal transmitted from the distant end of the cable will move the tongue of the relay to the right-hand or marking contact. Relays 114, 115, 116 and 117 are of the non-polarized type, the function of relay 114, which is controlled by the first unit of the received signal, being the selection of one of the two code combinations for each letter. Relays 115 and 116 are storing relays, their function being to store u the second and third received signal units or a" 125, which operatesthe printer mechanism to print the character selected, is illustrated diagrammatically. This printer may be any type of multiplex printer utilizing six permutation or selector magnets, and as these printers are well-known in the art, printer 118 will not be described in detail here.

Operation of aim magnet printer Assume that the receiving station is to receive the letters BE, the transmission of which was traced, and that the letter B, which consists of seven positive and one negative units, is now being received; that is, the tongue of relay 111 will lie against its spacing contact while brush 102 covers segments 103109, and the tongue of relay 111 will lie against its marking contact while brush 102 passes over segment 110. When the brush 102 passes over segment 103, acircuit will be completed from ground, positive battery 126, spacing contact of relay 111, conductor 127,.receiving ring 113, brush 102, segment 103, conductor 128, relay 114, conductor 129, positive battery 130 and ground. Since both sides of the winding of relay 114 are connected to battery of the same polarity, no current will flow through the winding of tact 147, releasing these relays. At the beginning of the next revolution of the distributor brushes, brush 112 passes over segments '148 and 149, as previously stated, and thereby momentarily energizes operating magnet 125, initiating the actual printing of the letter E.

fore carries an extra or seventh pair of transmitter contacts and a contact tongue 208 in addition to contact-tongues 202207. In-

stead of the single polar relay 26 of Fig. 2

which operated to place positive current on either side of the transmitter contacts, the seven-unit system shows two polar relays 226 and 227 which operate in-series to place negative polarity on oneside and positive polarity on the opposite side of the transmitter contacts. These polarities are reversed in accordance with the polarity of the last unit.

of the preceding code combination. Relay 31 of Fig. 2, which operated to place'positive or negative battery on the first transmittin segment, has consequently been dispense with and current is supplied directly to the first transmitter segment 216. Since there are seven tape transmitter contacts, the polarity of current to be passed to the sixth transmitter segment is determined by a pair of tape transmitter contacts and it is unnecessary, therefore to have a set of selecting relays, such as relays 39, 40 and 41 of Fig. 2, to select the polarity for this unit. By reason of the fact that different polarities are placed on the opposite sides of the transmitter contacts, it has also been possible to dispense with four of the re-transmitting relays of Fig. 2, as the contacts can be directly connected with the transmitting segments. The re-t'ransmitting relays 235,236 and 237 have been retained for the purpose of storing the last three units of the signal to be transmitted, thus permitting" the tape transmitter to step forward to the next letter at the same time that the signals are being transmitted. Polar relay 241 operates in series with relay 237 as in Fig. 2, to transmit the final polarity of the code combination to relays 226 and 227, thus determining which of the two code combinations is to be transmitted for the next letter. The contacts of all polarized relays shown are arranged so that current flowing through the windings from left to right moves the tongue to the left, and a current flowing from right to left moves the tongue to the right. This is assuming the movement of current from positive to negative. The distributor 209 is, in general,-the same for both systems. -It is not thoughtnecessary to consider the tape transmitter in detail here as it is identical with the standard tape transmitters in general use on multiplex te egraph circuits, except that it is equipped with seven sets of transmitter contacts and associated tongues, instead of the usual five or six.

Operation of seven-unit transm/ittz'ng cystem Assuming that the word BE is again to be transmitted over'this system, reference to the code in Fig. 1 will show that unit 8 is the only marking unit in this combination. Therefore, the perforated combination for the letter B will consist of a single perforation aligned so as to operate tongue 208 and when this combination is being sent out from 1 the tape transmitter 201, the tongues 202- 207 will be in the position shown in the drawing, while tongue 208 will be touching its lower -or marking contact. Assuming that the tongues of relays 226 and 227 are resting against their spacing contacts when transmitting brush 220 is passing over transmitting segment 216, positive battery will be applied to the cable over a circuit traced from ground, battery 229, conductor 230, spacing contact of relay 227, conductor 231, conductor 232 to segment 216, brush 215, ring 224 and conductor 225 to the cable. When brush 215 is passing over segment 217, positive current will be sent to the cable from the same source, since tongue 202 of the tape transmitter is resting against its upper or spacing contact which is connected to positive batter 229 over conductor 231 and spacing contact of relay 227. When the brush passes over segments 218, 219 and 220, positive current will be sent to thecable over similar circuits.

While brush 215 was passing over segments 216220, brush 214 was passing over segments 233, 234, 238, 239, 242 and 243 and connecting tongues 206, 207' and 208 to the windings of storing relays 235., 236 and 237, respectively.

Since tongues 206 and 207 are resting against their upper contacts which are connected with positive battery 229, by the time ground, positive battery 244, conductor 245,

left-hand contacts of relays 235 and 236 and conductors 246 and 247 to segments 221 and 222, respectively. The tongue of relay 237 will be resting against its right-hand or marking contact, since transmitter tongue 208 is touching its lower or marking contact, and negative battery will therefore be applied to segment 223 over a circuit sition. Relay 241 is used in connection Wlth the circuit for selecting the proper combination for the next character so that the first unit of the succeeding character will be of the same polarity as the final unit of the character last transmitted.

While brush 215 was passing over segments 221, 222 and 223, operating magnet 228 of the ta e transmitter was energized when the local rush 214 connected segments 251 and 252, closing a circuit from ground, battery 253, conductor 254, segments 251 and 252, conductor 255 and relay 228 to ground. The stepping forward of magnet 228 moved the tape so that the combination for the letter E is now set u on the transmitter. This stepping forwar of the tape transmitter does not multilate the signal being sent for the letter B, as units 6, 7 and 8 of the letter B have been previousl stored up on relays 235, 236 and 237. adle brush 215 was passing over segments 221, 222 and 223, the local brush 214 connected segments 289 and 290 and in doin so assed a current through relays 226 811C? 227 ii'om ground, battery 248, right-hand or marking contact of relay 241, conductor 256 conductor 257, seg ments 290 and 289, conductor 258, windings of relays 226 and 227 and ground, moving the armatures of relays 226 and 227 to their marking contacts to correspond with the setting of relay 241. The combination for the letter E is therefore now set up in the tape transmitter and transmitter tongues 202, 203, 204, 207 and 208 are resting against their upper contacts, and tongues 205 and 206 are resting against their lower contacts. When brush 215 passes over segment 216, negative battery will be applied to the cable over the following circuit: ground, negative battery 259, conductor 260, marking contact of relay 227, conductor 231 and conductor 232 to segment 216. When brush 215 passes over segments 217, 218, 219, negative battery will also be applied to the cable from the same source. During the time that brush 215 was passing over segments 216--219, the local brush 214 passed over segments 233 and 234, 238 and 239, and 242 and 243, and in doing so connected the tongues of transmitter contacts 206, 207, 208 to the windings of storing relays 235, 236 and 237 respectively, as previously traced. As tongue 205 will be in contact with its lower or marking contact, positive battery is passed from source 229 over conductor 261, marking contacts of repassed to this segment from current source 244 over conductor 245, left-hand contact of relay 235 and conductor 264 and so to the cable. Tongues 207 and 208 are lying against their upper or s acing contacts and negative current 1s there ore passed from battery 259 to the windings of relays 236 and 237 over circuits previously traced and the armatures of these relays are therefore moved a ainst their right-hand contacts so that when rush 215 passes over segments 222 and 223, negative current will be assed from battery 248 over conductor 249 t rough right-hand contacts of relays 236 and 237, conductors 247 and 250 to segments 222 and 223 and so to the cable. While brush 215 was passin over se ments 221, 222 and 223, local brus 214 e ected the operation of the tape transmitter operating magnet 228 and the re-setting of relays 226 and 227 from relay 241, as previously explained.

Description of seven-magnet printer rece'ixving system The circuits for the six-unit and sevenunit systems are identical with the exception of the printer used, and the connection for the sixth segment. Fig. 5 illustrates in diagrammatic form a seven-unit printer 318 which is substituted for the printer 118 of Fig. 3. Fig. 3 with this substitution thus shows a complete seven magnet printer receiving system. It will be seen that the only difference in the substituted printer is the addition of a seventh printer selecting magnet 354, which is placed between the fourth and fifth magnets and is connected to receiving segment 108, which was an unconnected segment in the six-unit receiving system of Fig. 3. Operation of seven-magnet printer receiving system The operation of the seven-unit receiving system is also identical with the operation of the six-unit receiving system, the only difference being that the sixth unit received on receiving segment 108 will be transferred directly to printer receiving magnet 554 and will, therefore, be utilized in making selections on the printer. The remaining operations will be readily understood from the tion.

opleration of the system disclosed in Fig; 3, w ich has already been discussed in detail.

What is claimed is:

1. In a communication system utilizing an eight-unit two element code having alternative code combinations of opposite polarity in which no impulse of single unit length occurs except at the beginning or end of a code combination, the method of transmitting a series of said code combinations so that no impulse of single unit length will occur in a message, comprlsing selecting each code combination so that the first unit of said combination is of the same polarityas the last unit of the preceding code combination.

2. In a communication system utilizing alternative code combinations of opposite polarity for each letter, the method of selecting one of said combinations, comprising the selection of the combination the first unit of which is of the same polarity as the last unit of the preceeding code combination.

3. In a printing telegraph system utilizing alternative code combinations of opposite polarity for each letter, the method of selecting one of said combinations, comprising the application to one side of all the contacts of a tape transmitter of a current having a polarity corresponding to that of the last signal unit of the preceding code combination.

4. In a printing telegraph system, the method of translating a six-unit two element code into an eight-unit two element code, comprising transmitting a preliminary signal selected independently of the six-unit code combination with which it is transmitted and of a polarity corresponding to that of the last unit of the preceding signal combina- 5. In a printing telegraph system, the method of translating a six-unit two element code into an eight-unit two element code, comprising transmitting a preliminary signal unit selected independently of the six-unit code combination with which it is transmitted and of a polarity corresponding to that of the last unit of the preceding signal combination and of transmitting an additional signal unit intermediate the fourth and fifth sig-- nal units of the six-unit code combination and of a polarity such that it will be identical in polarity with either said fourth or fifth signal unit.

6. In a printing telegraph system, the method of translating 2. six-unit two element code into an eight-unit two element code, comprising transmitting an additional signal unit intermediate two predetermined signal units of the six-unit code combination and of a polarity such that it will be identical with the unit either immediately precedin or immediately following it.

7 In a communication system, the method of operating a receiving printer by a code having alternative co e combinations of opposite polarit for each letter, comprising selecting one 0 said code combinatlons'in accordance with the polarity of the first repeived signal impulse of the code combina- 1on. i

8. In a printing telegraph s stem, the method of operating a rinter having six selector magnets by an-eigfit-unit two element code having alternative code combinations of opposite polarity for each letter, comprising utilizing the first received signal impulse of each code combination todetermine the polarity of the local current to be applied to the common return wire of the printer sele'cting magnets and the failure to utilize in any manner one of the received signal impulses.

9. In a printing telegraph system and in comblnation, a tape transmitter, a distributor, a plurality of re-transmitting relays jointly controlled by said transmitter and said distributor, a relay serially connected with one ofsaid relays, and a plurality of relays jointly controlled b said last-mentioned relay and said distributor to reverse the polarity of the current supplied to said transmitter.

10. In a printing telegraph system and in combination, a tape transmitter, a plurality of opposing contacts associated therewith, a relay connected with one side of all of said contacts, a plurality of relays operatively controlled by said transmitter, a transmitting distributor associated with said transmitter and with said relays, and, a relay jointly controlled by one of said last-mentioned relays and said distributor to apply current to either side of said transmitter contacts.

11. In a printing telegraph system, a tape transmitter, a plurality of opposing contacts associated with said transmitter, a relay connected with one side of all of said contacts, a distributor associated with said ransmitter, a plurality of re-transmitting r lays each operable under the control of a pair of said transmitter contacts, a plurality of re-transmitting relays each operable under the joint control of a pair of said transmitter contacts and said distributor, means for locking each of said last-mentioned relays, a selectingrelay serially connected with each of said lastmentioned relays, a single re-transmitting relay operable under the joint control of said selecting relays, a relay operable under the joint control of one of said selecting relays and said distributor and adapted to connect either side of all of said transmitter contacts with a source of current, means under the control of said distributor for unlocking said second-mentioned re-transmitting relays.

12. In a printing telegraph system, a tape transmitter, a plurality of opposing contacts associated with said transmitter, a distributor comprising a plurality of transmitting segments one of which is serially connected with one side of all of'said transmitter contacts, and a plurality of local segments, means for connecting certain transmitting segments with individual transmitter contacts, a plurality of relays each connected with one of the remaining transmitter contacts through local segments of the distributor and adapted to re-transmit signals to the remaining transmitting segments of said distributor, a pair of relays adapted to reverse the polarity of the current supplied to each side of said transmitter contacts,-and a relay signal impulses received over the rst receiving segment of said distributor and adapted 1 to place local current of the same polarity as the received signal impulse on the common return for all of said printer selecting magil nets, a plurality of storing relays each associated with one of said printer magnets,

means for locking said code selecting relay and said storing relays, a relay operably controlled by thedistributor for releasing said locking means, and a printer operating mag- 4 net operable under the control of said distributor.

14. In a communication system the method of translating a two element code having a predetermined number of units into' a two element code having a greater number of units, comprising transmitting an additional signal unit intermediate two predetermined signal units of the original combination and of a polarity such that it will be identical with the unit. either immediately preceding or immediately following it.

15. In a printing telegraph system the combination of a tape transmitter, a plurality of opposing contacts associated therewith, a relay operable under control of the last transmitted signal combination to place current on either side of all said contacts, a line, a

relay comm n to one side of all said contacts and operabl to place a current of predetermined polarity on the line.

16. In a printing telegraph system the combination of a tape transmitter comprising a plurality of opposing contacts, a plurality of relays operable under control of the last transmitted signal combination to place a current of predetermined polarity on, one side of all said contacts, a line and means for connecting said side of said contacts to said line.

17. In a printing telegraph system the com- J. bination of a plurality of retransmitting relays, a plurality of selecting relays severally operable under the control of said retransmit ting relays, and a retransmitting relay 0 erable under the joint control of a 1 said se ecting relays.

said receiving relay, to place either a ositive or negative potential on one side of al of said printer relays.

20. In a printing telegraph system, the method of operating a pr nter having seven selector magnets by an eight-unit two element code having alternative code combinations of opposite polarity for each letter, comprising selecting one of said code combinations in accordance wth the polarity of the first signal impulse of the code combination.

1 21. In a printing telegraph system, the method of operating a printer having six selector magnets by an eight-unit two element code having alternative code combinations of opposite polarity for each letter, comprising selecting one of said code combinations'in accordance with the polarity of the first signal impulse of the code combination and discarding another of said signal impulses.

In witness whereof, I hereunto subscribe my name this 31st day of March, 1931.

ALDER F. CONNERY. 

